geothermal heat pump economics: how the numbers … · geothermal heat pump economics: how the...

Geothermal Heat Pump Economics: How the Numbers Really Work

Demystifying the Costs & Benefits ofGeothermal Heating & Cooling Systems

PRESENTER:Mark Sakry, CGD

Northern GroundSource Inc.www.NorthernGroundSource.com

In accordance with the Department of Labor and Industry’s statute 326.0981, Subd. 11,

“This educational offering is recognized by the Minnesota Department of Labor and Industry as satisfying 1.5 hours of credit toward Building Officials and Residential Contractors code/energy continuing education requirements.”

For additional continuing education approvals, please see your credit tracking card.

1. The Geothermal Heat Pump ConceptThe Simple Logic of a “Ground Source” Approach & Its Ultimate Benefit

Heating Remains #1 U.S. Home Energy Need!

How we use energy in our homes. Heating accounts for the biggest portion of your utility bills. Source: U.S. Energy Information Administration, AEO2014.

A common air conditioner is a simple Air-to-Air Heat Pump—exchanges 74°F indoor air with outdoor temperatures that fluctuate broadly and can often swing to over 100°F.

An air source heat pump adds Air-to-Air heating capability—it exchanges 70°F indoor air with outdoor temperatures that can swing well below 20°F (common ASHP operating range limit).

DULUTH SOIL STATISTICS:

MEAN SURFACE TEMPERATURE 1 ft.= 41°F

ANNUAL SWING= 28°F

DAYS TO MINIMUM = 37

DEEP EARTH TEMPERATURE= 48°F

–20 –10

41°F

+10 +20

481216202428

depth, ft

groundtemperature, °F

average soil(0.6 ft²/day or 0.025 ft²/hr)

48°F

0

55°F27°F

48°F34°F

Stable

Where might we find temperatures nearby that are moderate and stable all year round?

Heat pump technology logically goes…underground! (Video)

Heat pump technology logically goes…underground!

All GHP System Mechanical Equipment is Located Inside.

High Grade Geothermal Energy

Old Faithful Geyser “Hot Rocks” Power

Low Grade Geothermal Energy

“Solar” Geothermal GeoExchange Systems

Lower heat from the ground is “concentrated”

…into higher heat for distribution inside structure

…only a slight energy "penalty" to run the electric motors of a compressor, a couple small pumps and a blower.

Basic Concept: Geothermal Heating

Introducing:The CompressorThe Compressor is the GHP’s primary working unit where gas is compressed, heated, and “pumped” to its heat exchange delivery point.

A refrigerant gas (with much better heat concentrating properties than air) is used.

SCROLL: TOP VIEW

SCROLLCOMPRESSOR

Zeroth Law of Thermodynamics

WIKIPEDIA: When two systems…are brought in diathermic contact with each other they exchange heat to establish a thermal equilibrium between each other.

Heat moves to Cold…Always!

Typical Forced Air GHP System

Air Loop

Ground LoopRefrigerant Loop

Domestic Hot Water Loop

11,245 kWh

38,008 kWh

ULTIMATE BENEFIT: OVER 70% OF HEAT ENERGY IS FROM GROUND!

70%

0.12 $/kWh

0.12 $/kWh

$2.39/gal

$3.699/gal

$0.99/Therm

$1,739.38GSHP

$4,461.98RH

$1,955.18Nat. Gas

$3,866.15Propane

$4,357.72Fuel Oil

ANNUAL ENERGY COSTS FOR TYPICAL 4 TON HOME IN DULUTH

2. What Does a Geothermal System Cost?Examining the main factors that determine GHP system cost.

2. What Does a Geothermal System Cost?Examining the main factors that determine GHP system cost.

How much is a car?

GHP System Cost Factors GHP System Sizing Site Geology &

Conditions Delivery System

Preferences GHP Configuration

Electric Power Requirements

Incentive Programs

Quality of Equipment

Quality of Installation

GHP System Sizing• The first most critical step in establishing

GHP system cost is accurate system sizing

• Proper sizing is achieved by first establish-ing the peak heating load of the structure (peak cooling load is used in South)

• As peak load increases, so does GHP system sizing requirement…and therefore cost.

Accepted Load Calculation Standard:Use “Manual J” Referenced SoftwareIN GENERAL: As heat requirement increases—GHP system sizing increases proportionately…along with the total system design and installation cost!

Alternate Load Method (Retrofits):Based on Fuel/Electric Usage History

Duluth Home5,300 sq’ = 70,000 BTUH

Finland Community Center10,000 sq’ = 160,0,000 BTUH

Consider that GHP installation costs and benefits are scalable!

A 6T home built in Foxboro, WI might be a 7T home in Babbitt, MN

Foxboro, WI = 60,000 BTUH Babbitt, MN = 70,000 BTUH

A “Ton” is a long-established British thermal unit we still use

1 Ton (British) = 12,000 BTUHBUT…

A cold climate GHP system might have a design output of only

10,000 BTUH/Ton

GHP output depends on the fluid temperature entering from the loop

EXAMPLE 1:5 Ton GHP (SM060)60,300 BTUH Output @ 50°F EWT48,000 BTUH Output @ 32°F EWT

The colder the fluid temperature from the loop…the lower the output of the GHP

Loop Sizing Follows Peak Heating Load…Not Just GHP Capacity!

EXAMPLE 2:Horizontally-trenched loop circuits for cold climate GHP systems:1 Loop ≈ 8,000 to 10,000 BTUHPEAK TON

Approx. 1 loop circuit of sufficient length for every 10,000 BTUH of the peak heating load

Peak heating Load = 49,537 BTUH(Future Insulation = 41,761 BTUH)4.0<5T GHP (TVC048) @ 30°F EWT = 45,500 BTUH

Site Geology & Conditions• One of the most limiting factors in

determining GHP system cost is site geology and conditions

• A primary objective is to achieve maximumGHX performance benefit at minimal cost and impact to site

• Different kinds of loops come at different cost… and mostly achieve the same result

Common GHX Options by Increasing Cost:

Open Loop / Pump & Dump Existing Pond & Lake Loops Horizontally Trenched or Excavated Excavated Pond Loop Horizontally Drilled Vertically Bored in Deep Soil/Overburden Vertically Bored in Rock

Common GHX/Loop Options

Open Loop / Pump & Dump Systems

Instead of a buried closed loop GHX, domesticwater from house is simply pumped through the GHP coil then discharged somewhere outside. (Pictured is a simple shallow drain tile in sand.)

Main Cost Factors: Well must have sufficient recovery rate Size of well pump might slightly increase Cycle-stop or variable speed pump often

specified (driller advises) Flow control assembly required at GHP Discharge pipe trench & site drainage State water use limits may eliminate

option (MN: 10K gal/day—1M gal/year)

Open Loop / Pump & Dump Systems

Existing Pond & Lake Loops

Main Cost Factors:

Lake permits difficult to obtain, usually ruled out as option if other options exist

Pond expansion sometimes required Less loop pipe but more labor and other

materials for weighting and containment Ground loop excavation eliminated, but

still requires a S/R pipe trench

Existing Pond & Lake Loops

Closer Spacing = longer pipe requirement, smaller consolidated excavation footprint (500 ft2/T)

Wider Spacing = shorter pipe requirement, expanded excava-tion footprint (1,000 ft2/T)

Horizontally Excavated

Main Cost Factors:

Excavation cost…per site conditions! Unknown or unforeseen encumbrances Loop size and configuration (at roughly 1

loop circuit per 10K BTUH of peak load) Largest footprint, greater impact to site Finished landscaping and vegetation

(excavation is commonly rough-in only)

Horizontally Excavated

Pond Heat Exchangers combine exceptional GSHP system performance…

With an aesthetic component you just can’t get from a con-ventional earth loop.

Excavated Pond

Main Cost Factors:

Possible wetland concerns Loop footprint roughly same as an

excavated GHX Must deal with displaced soil material Additional containment materials or 1’-2’

sand/gravel backfill required

Excavated Pond

Horizontally Drilled

HDD Machine Drilling 150 Ton GHEX for a

Minnesota School

Main Cost Factors: HDD loops minimize site impact but

usually cost more per design Ton than excavated loops (machine time & grout)

Unknown or unforeseen encumbrances Loop size and configuration by qualified

designer using design software Some excavation still required if manifold

is buried (interior manifold also adds cost)

Horizontally Drilled

Vertically Bored in Deep Soil

Main Cost Factors: Vertically bored ground loops may require

less pipe than HDD but usually cost more for machine, crew and grout

Depth of unconsolidated overburden Loop size and configuration by qualified

designer using design software Excavation required to connect loops,

impact determined by bore field footprint

Vertically Bored in Deep Soil

Vertically Bored in Rock

Main Cost Factors: Drilling through dense rock requires

heavier equipment than “mud” drilling, typically at higher cost (including grout)

Depth of overburden for extracting casing Loop size and configuration by qualified

designer using design software If header excavation is over shallow rock,

a costly insulation detail may be required

Vertically Bored in Rock

Delivery System Preferences• Geothermal heating is inherently a low-

temperature technology

• Heat delivery systems must conform to GHP temperatures not the other way around

• Combining hydronic radiant heating with forced air heating and/or cooling generally adds cost to the GHP system itself

• GHP system configuration follows delivery system preferences if they are compatible

The “geothermal system” is generally assigned to the “supply” side of heating/cooling functions.

Supply Side (GSHP) Delivery Side (HVAC)

Ground Heat Exchanger (GHX)

Ground Source Heat Pump (GSHP or GHP)

Loop Pump or Flow Center

Some Peripheral and Auxiliary Components (incl. Controls)

Duct System (incl. Air Exchanger)

Radiant Floor Tubing, Manifolds, Zone Pumps and Controls

Radiant Baseboards, Panels, Radiators

Plumbing/Piping Delivery Systems

High Temp versus Low Temp?

High Temp @50,000 BTUH!

Low Temp @50,000 BTUH!

130°F - 180°F 85°F - 115°F

GENERAL PREMISE: The Lower the Temperature—the Higher the Efficiency!

High Temp @50,000 BTUH!

Low Temp @50,000 BTUH!

GHP Configuration

GHP ConfigurationGHP SYSTEM COST OPTIONS—33,645 BTUH HOME:(Not including any HVAC 'delivery' side costs)

3.0<4T Forced Air Heating & CoolingRequires full house duct system only.

$18K GHP/GHX + Approx. $3.5K Excavation = $21.5K

3.0<4T Hydronic Heating OnlyRequires radiant floor tubing only but some minimal ductwork for ventilation system.


3.0<4T Hydronic Heating & Cooling (Split System)Requires radiant floor tubing plus medium sized duct system.


GHP ConfigurationGHP SYSTEM COST OPTIONS W/GARAGE ADDED(Not including any HVAC 'delivery' side costs)

5.0T Hydronic Heating OnlyRequires radiant floor tubing only but some minimal ductwork for ventilation system.

$22K GHP/GHX + Approx. $4K Excavation = $28K

5.0T Hydronic Heating & Cooling (Split System)Requires radiant floor tubing plus medium sized duct system for house.


GHP ConfigurationGHP SYSTEM COST OPTIONS W/GARAGE ADDED(Not including any HVAC 'delivery' side costs)

5.0T Hydronic Heating OnlyRequires radiant floor tubing only but some minimal ductwork for ventilation system.


5.0T Hydronic Heating & Cooling (Split System)Requires radiant floor tubing plus medium sized duct system for house.


COST SCALES: $21.5K > $23.5K > $28K > $28.5K > $31K

State-of-the-Art 2-Stage Forced Air GHP System Installation

Older Generation Stand-Alone Combined F/A & HYD GHP System

Stand-Alone Forced Air GHPs

Main Cost Factors:

The higher the GHP Ton, the higher the fan velocity @ 400 CFM/Ton heating load!

Ductwork sizing and expense increases proportionately by Forced Air GHP Ton

3 Ton GHP @ 400 CFM/Ton = 1,200 CFM4 Ton GHP @ 400 CFM/Ton = 1,600 CFM5 Ton GHP @ 400 CFM/Ton = 1,200 CFM6 Ton GHP @ 400 CFM/Ton = 2,000 CFM

Stand-Alone Forced Air GHPs

HYD Heat Only GHP System

Main Cost Factors: No ductwork, low-temp radiant heat only Cannot use baseboard, radiators, or

staple-up tubing—must use slab, gypsum or some other top-of-floor assembly

Added hydronic thermal storage (buffer) tank, GHP primary pump(s) and controls

If Interruptible Dual Fuel (IDF) system, integrated sidearm gas boiler preferred

HYD Heat Only GHP System

Split GHP System (DX)

Main Cost Factors:

GHP includes DX A-coil for installing inside plenum of gas furnace or other air handler, which are bought separately

Ductwork can often remain sized to furnace blower, typically only 1,200 CFM

Eliminates need for outdoor AC/ASHP unit Works well for Dual Fuel, but GHP shuts

off with any 2nd stage call for gas heat

Split GHP System (DX)

HYD Split GHP System

Main Cost Factors:

Among the most advanced and versatile GHP configurations, but also more costly

Hydronic air handler/fan coil and controls Stainless steel/foam pump packs and pipe

insulation for chilled water cooling Works exceptionally well for Dual Fuel and

2nd stage with integrated sidearm boiler

HYD Split GHP System

GHP Power Requirements• The GHP compressor is basically a “small

motor” and uses the most energy on the system—demand increases with GHP size

• Fluid pumps and blowers are secondaryconsumers on the GHP system

• Electrical infrastructure must meet the entire demand of the system including LRA!

• You can run a residential GHP on a small generator, but you can’t start it

GHP Power Requirements

• Electric data for a specific GHP model or series is provided in the engineering manual of most manufacturers

• Data typically includes amperage for compressor, blower, external pump(s) and the desuperheater pump

GHP Incentive Programs• Utility Rebate Programs

• 30% Federal Tax Credit (through 2016)

• GHP Installation Financing Programs

• Also consider that geothermal heating and cooling may still offer a good Return on Investment (ROI) even without these!

2016 Geothermal Rebate Programs Minnesota Power

$200/T Closed Loop ($100/T Open Loop) + $200 ECM[Bonuses Frequently Offered: $50/T GSHP + $50 ECM or $100/T & ECM for Triple-E Home]http://www.mnpower.com/EnergyConservation/GSHPIncentivePackage

Great River Energy Affiliates:$400/T Closed or Open Loop ($200/T from East Central Energy) + $100 ECM

Cooperative Light & Powerhttp://www.clpower.com/pdfs/2013GSHP.pdf

Lake Country Powerhttp://www.lakecountrypower.coop/viewpage.php?pagename=ratesandrebates

East Central Energyhttp://www.eastcentralenergy.com/PDFs/gshprebate2014.pdf

Arrowhead Electrical Cooperativehttp://www.aecimn.com/wp-content/uploads/2013/02/GSHP-Geothermal-2013-Rebate.pdf

Wisconsin Focus On Energy Program:$650 Flat Geothermal Rebate from Participating Utilities for Retrofitshttp://www.focusonenergy.com/residential/renewable/geothermal-heat-pumps

Geothermal Heat Pump Residential Tax Incentives

Federal Income Tax Credit: 30% of total geothermal system cost Credit capped at $2,000 for 2008 Credit unlimited for 2009 through 2016 Can be used to offset AMT tax Can be combined with other tax credits Can be used in more than one year

Eligibility: Home must be located in U.S. Includes houses, cooperatives, condos, mobile homes Does not have to be your main house GSHP must meet Energy Star requirements Must be placed in service between 1/1/2008-12/31/2016

Geothermal Heat Pump Business Tax Incentives

Federal Income Tax Credit: 10% of total geothermal system cost Credit is not limited Can be used to offset AMT tax Can be used in combination with subsidized financing Can be used in more than one year

Accelerated Depreciation: 5 year MACR depreciation of entire system Eligible for bonus depreciation in 2009 (50% write-off in first year)

Eligibility: Building must be located in U.S. Original use begins with taxpayer Must be placed in service between 10/3/2008-12/31/2016 Can be used by regulated utilities Must be claimed by owner of property (effects non-taxable)

Loan Terms: Loan amounts up to $20,000 4.99% fixed interest rate (5.385% Annual Percentage Rate*) No maximum income limit Terms up to 10 years This loan is secured by a mortgage on the property. Closing costs apply

Property Eligibility: Single family, owner-occupied, primary residence Properties under construction or held in Trust are not eligible

Types of Improvements: Eligible improvements include: ground source heat pumps that meet or

exceed Energy Star 1 efficiency requirements; heat pump water heaters and air source heat pumps that are Energy Star qualified

*APR is based on $20,000 for 10 years.

2016 Geothermal Financing ProgramsCenter for Energy and Environment (MN)

http://mncee.org/Find-Programs/Geothermal-Financing/

Loan Terms: Loan amounts up to $7,500 and up to $25,000 at… 0% - 2.9% financing respectively! No family income limits Terms up to 10 years Loans must be secured via a mortgage against the property not to exceed

$25,000 or up to 100 percent of the property value

Property Eligibility: Dwelling must be a residential, one-unit, owner-occupied property Member must be in good standing with the utility

Types of Improvements: Eligible improvements include: ground source heat pumps that meet or

exceed Energy Star 1 efficiency requirements; heat pump water heaters and air source heat pumps that are Energy Star qualified; electric thermal storage (ETS) space and water heating systems with some restrictions.

2016 Geothermal Financing ProgramsCEE Loans Sponsored by Utility Partners

http://www.mnbrighterideas.com/financing/cee.cfm

Quality of Equipment

Quality of Installation

3. What Determines GHP System Benefit?Examining the main factors that determine GHP economic benefit.

GHP Benefits Determined By: Climate (Moderate vs

Extreme) Current Energy Rates &

Inflation GHP Capacity to Peak

Load Adequacy of HVAC

Distribution System Life Cycle Warranty & Service

Distance Alternative Equipment

Cost Loan Interest GHP System Cost

Recovery

16,765 kWh

56,163 kWh

Source: U.S. National Oceanic & Atmospheric Administration (NOAA).

Climate Moderate vs Extreme

How we use energy in our homes. Heating accounts for the biggest portion of your utility bills. Source: U.S. Energy Information Administration, AEO2014.

STATE AVERAGE TEMP(2014)

U.S. RANK(2014)

ALASKA 30.1° F 49

MINNESOTA 38.6° F 48

NORTH DAKOTA 39.0° F 47

WISCONSIN 40.2° F 46



9,817

180

Current Energy Rates…

…and Inflation

GHP Capacity to Peak Load

GHP Capacity to Peak Load(Peak Load = 73,182 BTUH @ -20°F OAT / 70°F)

GHP Capacity to Peak Load(IDF @ 0.06 $/kWh w/LP Backup @ $2.899/gal)

GSHP Sizing Rules of Thumb

Cooling-Dominant Derived Rule: Do not size GHP heating capacity more than 25% above the cooling load (impractical?)

Manufacturer-Derived Rule: Do not size GHP to less than 85% of the peak heating load (roughly 1 Ton undersizing)

Cold Climate Sizing Trend: Size to perform 96-100% of all the heating (but consider sizing scale-back for honest “hardships”)

4.0<7T Vertically Bored GHP System @ 62.2% GHP Sizing

GHP Capacity to Peak Load(Peak Load = 73,167 BTUH @ -20°F OAT / 70°F)

GHP Capacity to Peak Load(Full Residential Electric Rate @ 0.120 $/kWh)

Adequacy of Distribution

Adequacy of Distribution• Low-temp GHP (refrigeration) technology

likes to maintain system balance withoutbeing called on to perform extreme tasks

• Sufficient and adequately distributed air flow is vital for comfort, as well as proper air coil performance and heat exchange

• Continuous low speed ECM fan is extremely beneficial for air quality, efficiency and comfort!

System Life Cycle• With the newer GHP technologies, most

manufacturers now project a design life 25 to 30 years…if the GHP system is properly designed, installed and maintained

• EPA life cycle rating for geothermal HDPE pipe is 200 years

• Life cycle varies for secondary components, such as circulating pumps, blowers and some electrical parts

Warranty & Service Distance• To meet Energy Star Tier 3 standards, the

EPA now requires GHP manufacturers to warranty all parts and labor for 5 years

• Many manufacturers also offer an additional 5 years for refrigeration parts only (without labor) and/or “lifetime” compressor

• Because GHP technology is specialized, non-warranty service work can cost more, and a qualified technician may not be close by

• Alternative equipment is the heating and cooling equipment that would otherwise be installed at lesser cost (furnace, boiler, AC)

• Conventional HVAC equipment costs vary widely, but there is ultimately some netdifference in cost to upgrade to geo’

• GHP system cost recovery calculations mustconsider alternative equipment costs for a true assessment of GHP economic benefit!

Alternative Equipment Cost


How much more is a GHP system compared to the alternative?


Cost difference between RH Thermal Storage & 7T GHP system

Interest

Cost difference between RH Thermal Storage & 7T GHP system

• SIMPLE PAYBACK—how long it takes for the net upgrade cost of the GHP system to be fully recovered using current energy rates

• SHORT TERM SAVINGS—snapshot of annual and monthly savings with incremental loan interest taken into account

• 30 YEAR SAVINGS—difference in cost of ownership between a conventional HVAC system and GHP system over 30 years

GHP System Cost Recovery

0.06 $/kWh

0.05 $/kWh

$2.899/gal $3.699/gal

SIMPLE PAYBACK

$1,492.84GHP (IDF)

$2,945.20RH (Off Peak)

$6,563.27Propane

$6,615.06Fuel Oil

SIMPLE PAYBACK

SHORT TERM SAVINGS

30 YEAR SAVINGS

LIFETIME SAVINGS!

Over 70% of home’s heating energy needs will be FREE forever.

16,765 kWh

56,163 kWh

DON’T FORGET…ENVIRONMENTAL “SAVINGS”

70%

END

RESOURCES:

Northern GroundSource Inc.www.ColdClimateGeothermal.com

International Ground Source Heat Pump Associationwww.igshpa.okstate.edu

Minnesota Geothermal Heat Pump Associationwww.MNGHPA.org

Wisconsin Geothermal Associationwww.wisgeo.org

GeoExchangewww.GeoExchange.org

Association of Energy Engineerswww.aeecenter.org

geothermal heat pump economics: how the numbers … · geothermal heat pump economics: how the...

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